LIFE-HISTORIES AND THEIR LESSONS, 265 

ments which constitute our recent knowledge of minute life, and 
all the facts which have enabled recent science to formulate the 
magnificent generalisation which finds in protoplasm the physical 
basis of life. 
I have in my possession some fragments of a wooden hutch 
which was used by me for many years as a shelter for offensive 
putrefactions, from which septic organisms of various kinds were 
derived for study. A month ago I sawed and filed some of this, 
and placed it with minute broken fragments of the same wood 
into a vessel with water, and a little of Cohn’s nutritive fluid, which 
was kept at a temperature of 62°F. In Plate V., Fig. 18 a, I show 
the result of. the examination of a minute drop of the surface film 
after four days, where the earliest forms of Bacteria are in vast 
abundance, and in the drop were intensely active.* At 2 the 
same fluid is seen more generally examined four days after, when 
Baallus lineola, B. ulna, and even Spirillum volutans struggle with 
B. termo, and prevail; and a few early developments of monads 
appear. In the quadrants 3 and 4 the general result of examina- 
tion on the twelfth and sixteenth day are manifest, and all these 
forms were the common forms upon which, at the time, this out- 
door cupboard was employed for the protection of the infusions on 
which Dr. Drysdale and myself were at work. It was simply 
evidence of what has been often given before, that the germs of 
the putrefactive organisms can persist in air undeveloped ; but on 
entering a suitable fluid, are at once stimulated into development 
and increase. The wood of the cupboard was charged with germs. 
These were the germs of forms whose life-histories in many cases 
were known. ‘They succeeded each other in time ; they did not all 
appear together; but this, so far as we at present know, is dependent 
upon the condition of the fluid as superinduced by the forms that 
have gone before. Certain it is that their life-cycles are inde- 
pendent of each other. The monads are no more “ transmuta- 
tions” of the bacteria, than the graylings and trout of the Upper 
Thames are “transmutations” of its sticklebacks and minnows. 
It will complete the evidence which I have sought to give as to 
the need of caution in relation to hasty inference in the study of 
the minuter forms of life, if I take a case of its wise exercise from 
no older a source than the Quarterly Journal of Microscopical 
Science for April of this year (1880). It is furnished by Mr. Sid- 
dall in a paper “On Shepheardella, an undescribed type of Marine 
Rhizophoda.”+ It is a curious marine organism, seen in Fig. 1, 
Plate VI., which Mr. Siddall points out has a similarity of external 
form with the Gregarina gigantea of Van Beneden. But the ob- 
* Only a quadrant of the “ field ” in each case is shown, 
+ Page 129, ef seg. 
F a ; 
